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                [Wf2014]Crane Balancing                </h1>
                <p>时间限制：1s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：128MB</p>			</div>
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                                <h3>题目描述</h3><p><p>&nbsp;<span style="text-indent: 21pt; font-family: 宋体;">作为刚刚从蓝翔毕业的优秀学子，你成为了一名吊车司机。在施工作业中，你必须时刻保证吊车的平衡，如果吊起的重物太重或太轻，你的吊车就会因失去平衡而倒下。现在，</span><span lang="EN-US" style="text-indent: 21pt;">ACM(The Association of Crane Manufacturers)</span><span style="text-indent: 21pt; font-family: 宋体;">公司准备请既会玩吊车，又能码代码的你来设计一款吊车平衡计算软件。为了方便起见，我们将吊车视作一个密度均匀的</span><i style="text-indent: 21pt;"><span lang="EN-US">n</span></i><span style="text-indent: 21pt; font-family: 宋体;">边形，其顶点依次标号为</span><span lang="EN-US" style="text-indent: 21pt;">1...<i>n</i></span><span style="text-indent: 21pt; font-family: 宋体;">，挂载重物的吊钩就是</span><span lang="EN-US" style="text-indent: 21pt;">1</span><span style="text-indent: 21pt; font-family: 宋体;">号点。现在要在<b><u>编号为</u></b></span><b style="text-indent: 21pt;"><u><span lang="EN-US">1</span></u></b><span style="text-indent: 21pt; font-family: 宋体;">的端点放上一个<b><u>大小忽略不计</u></b>的重物，问放的重物的重量在什么区间内，才能使这个多边形保持平衡</span><span lang="EN-US" style="text-indent: 21pt;">(</span><span style="text-indent: 21pt; font-family: 宋体;">不会往左或往右翻</span><span lang="EN-US" style="text-indent: 21pt;">)</span><span style="text-indent: 21pt; font-family: 宋体;">。<br />
</span></p>
<p class="MsoNormal"></p></p><hr/><h3>输入格式</h3><p><p><span style="font-family: 宋体;">输入数据的第一行是一个整数</span><i><span lang="EN-US">n</span></i><span style="font-family: 宋体;">，代表这个多边形的边数。<span style="font-family: 宋体;">之后</span><i><span lang="EN-US">n</span></i><span style="font-family: 宋体;">行，每行两个整数，依次代表这个多边形的第</span><span lang="EN-US">1</span><span style="font-family: 宋体;">号点、第</span><span lang="EN-US">2</span><span style="font-family: 宋体;">号点</span><span lang="EN-US">......</span><span style="font-family: 宋体;">第</span><i><span lang="EN-US">n</span></i><span style="font-family: 宋体;">号点的坐标</span><br />
</span></p></p><hr/><h3>输出格式</h3><p><p>&nbsp;<span style="font-family: 宋体;">输出只有一行，代表吊起的重物质量的闭区间</span><span lang="EN-US">[<i>a,b</i>]</span><span style="font-family: 宋体;">，注意<b><u>左端点向下取整，右端点向上取整</u></b>。例如，如果区间为</span><span lang="EN-US">[1.5,13.3]</span><span style="font-family: 宋体;">，则<b><u>输出</u></b></span><b><u><span lang="EN-US">1 .. 14</span></u></b><span style="font-family: 宋体;">。若区间为</span><span lang="EN-US">[<i>a</i>,+</span><span style="font-family: 宋体;">&infin;</span><span lang="EN-US">)</span><span style="font-family: 宋体;">，则<b><u>输出</u></b></span><b><i><u><span lang="EN-US">a</span></u></i><u><span lang="EN-US">&nbsp;.. inf</span></u></b><span style="font-family: 宋体;">。如果吊车不能承载任何质量的重物，则<b><u>输出</u></b></span><b><u><span lang="EN-US">unstable</span></u></b><span style="font-family: 宋体;">。</span></p></p><hr/><h3>样例输入</h3><pre>7
50 50
0 50
0 0
30 0
30 30
40 40
50 40
</pre><hr/><h3>样例输出</h3><pre>0 .. 1017
</pre><hr/><h3>提示</h3><p>没有写明提示</p><hr/><h3>题目来源</h3><p>鸣谢qpswwww提供译文</p>
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